The goal of this research is to relate the chemical properties of tentoxin, including conformation and structural variations to its mechanism of action. Tentoxin is a cyclic tetrapeptide possessing the unusual alpha, beta-unsaturated aminoacid N-methyl-dehydrophenylalanine. Research is proceeding simultaneously toward two goals: the chemical synthesis of tentoxin and its analogs; and the determination of its mechanism of action. Because the conformation of tentoxin can be readily studied by NMR it is planned to determine conformational changes of the ring system as ring substituents are changed, and to relate these changes to altered biological activity.